1. Field of the Invention
This invention relates to a means to improve the performance of a propeller driven power boat.
More particularly, this invention relates to a method and means to neutralize the undesirable propeller forces, such as side thrust loads, thereby trimming the boat to obtain better performance.
2. Description of the Prior Art
Propeller driven power boats of all kinds are disadvantaged in that they all produce a certain amount of non-productive thrust loads when the propeller is driven through the water.
This phenomenon is explained by the following example. When the propeller is turning in a clockwise direction (the propeller may turn in either direction) with a blade of the propeller passing through about the four o'clock position to about the eight o'clock position, it generates side thrust loads that tend to push the stern of the boat to the right. In other words, the rotation of the blade from about the four o'clock to the eight o'clock position causes the stern of the boat to yaw to the right, turning the bow of the boat to the left; hence, the helmsman must correct to the right to compensate for the yaw condition of the boat. The rotation of the lower propeller blade encounters water that is more dense because it is at a greater depth than the water encountered by the upper blade during its' rotation, thus it drives the stern to the right due to the greater resistance offered by the more dense, deeper water.
In high speed racing boats, such as a deep V or a hydroplane, where tremendous horsepower is transmitted to the propeller, the undesirable side producing loads are even more pronounced. The constant rudder correction to compensate for the yaw producing tendency of the propeller produces a drag condition that slows down the boat. Aside from the increased drag, the boat is extremely difficult to hold on a course which obviously is both dangerous and fatiguing to the driver of the boat.
Where counter rotating twin propellers are utilized in some boats, the yaw producing side loads are cancelled out, one against the other. However, these loads still exist which tend to pull the propeller shafts together or to push them apart (depending on their rotation) and thus collectively subtract from the forward producing thrust of each propeller in the twin screw arrangement.
The present invention substantially converts the undesirable propeller loads, such as side producing thrust of a boat's propeller to forward thrust, resulting in an increase of boat performance without increasing the horsepower level of the propulsion unit.